Postgres could not connect to server
Had a similar problem; a pid file was blocking postgres from starting up. To fix it:
$ rm /usr/local/var/postgres/postmaster.pid$ brew services restart postgresqland then all is well.
This can sometimes be an issue with a postgres upgrade.
In my case, it happened when upgrading from 9.3 to 9.4.
See http://www.postgresql.org/docs/9.4/static/upgrading.html
OS X/Homebrew:
Try running postgres -D /usr/local/var/postgres -- it will give you a much more verbose output if postgres fails to start.
In my case, running rm -rf /usr/local/var/postgres && initdb /usr/local/var/postgres -E utf8 removed my old databases and then reinitialized the postgres db schema.
Thanks to https://github.com/Homebrew/homebrew/issues/35240 for that solution.
After regenerating my databases (with rake db:create) everything worked fine again.
Found a solution that worked for me here:
You basically run the following command to manually start the server:
pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start